The invention relates to a protective cover for an optical disc.
Optical discs have been in use since the early 1980""s and have largely replaced vinyl phonograph records as a major medium for recording and playing back of audio information. Optical discs currently come in multiple different forms. Compact discs (CDs) are commonly used to record music. CD-ROMs are commonly used to record data for use by personal computers. Digital versatile discs (DVDs), which have an even larger capacity to store data than CDs and CD-ROMs, are commonly used to record video as well as large amounts of digital data for other purposes. There are other types of optical discs including: CD-Rs on which a user can write, but not re-write, information; CD-RWs on which users can both write and re-write data; and laserdiscs, an old, large-sized optical disc for recording video programming. It is probable that there will be new types of optical discs in the future from which recorded information can be read by light.
Optical discs have many benefits. They are much smaller than many other products capable of storing an equal amount of data. Often their data can be read with virtually perfect accuracy despite the presence of dust. This is due, in part, to their recording of redundant information to help them correct minor reading errors. And since they are read optically, the process of reading them does not wear out their data recording surfaces. Unfortunately, however, scratches on the surface of an optical disc can reduce the ability of the laser circuitry that reads such discs to track or read data on the disc, making all or a portion of such an optical disc unreadable.
An optical disc is comprised of two sides. Both are important in the laser circuitry""s ability to read information encoded on the disc.
The read, or data, side is read by the laser circuitry directly by focusing a light beam on a very small point on the disc and xe2x80x9creadingxe2x80x9d small pits or impressions which represent the 1""s and 0""s that make up the data stream that encodes audio, video, or data information. Any substantial scratch in the clear coating on the read side of the disc can undesirably block or deflect light, causing the laser circuitry to misread data or become confused as to where it is in the context of the binary data stream. This can cause the player to play the same block of data repeatedly, which, in the case of an audio CD, produces a sound similar to the xe2x80x9cskippingxe2x80x9d which commonly occurred in the playback of scratched vinyl records. In some cases such scratches can force the playback of the optical disc to stop entirely.
The second side of an optical disc, the xe2x80x9clabelxe2x80x9d side, does not record laser-readable information, but it does serve an important role in the playback of such information. In addition to providing a surface upon which a label for the disc can be written or printed, the label side has a thin reflective layer needed to provide a relatively even reflective background to the layers of the disc""s read side on which information is recorded. This relatively even backdrop for the data side allows the laser circuitry to more easily discern between 1 and 0 bits.
A scratch on the label side deep enough to tear into its reflective layer can render its disc unreadable. This condition can be observed by holding the optical disc up to a light source and viewing the holes in the reflective layer allowing light to pass through.
It is an object of the invention to provide a protective cover for optical discs that helps protect them from damage due to scratching.
It is another object of the invention to provide such a protective cover that is relatively easy to mount onto an optical disc.
It is yet another object of the invention to provide such a protective cover that tends to remain on an optical disc once it has been mounted on that disc.
It is still another object of the invention to provide such a protective cover that is relatively easy to remove from an optical disc once it has been mounted on that disc.
According to one aspect of the invention, an optical disc protector is provided for being mounted upon and protecting at least one side of an optical disc. The protector includes a circular main surface and a peripheral lip. The circular main surface has a diameter the same as, or slightly larger than, the optical discs on which the protector is designed to be mounted. The main surface is in the form of a sheet that has two substantially parallel sides: a disc-facing side intended to face the optical disc upon which the protector is mounted, and an exterior-facing side that is intended to accept the damage from mishandling on behalf of the optical disc. The main surface is made of an optically clear material, so as not to interfere with the reading of data from an optical disc upon which the protector has been mounted. The main surface also has a hole in its center to allow an optical disc upon which such a protector is mounted to be used in an optical disc reader. The peripheral lip is attached to, and extends all the way around, the perimeter of the circular main surface. The peripheral lip extends away from the perimeter of the disc-facing side of the main surface at an inward angle towards the center of the optical disc protector. As a result, the diameter of the peripheral lip at its end furthest from the main surface is smaller than the diameter of the main surface and of the optical discs on which the protector is designed to be used. The peripheral lip is flexible so as to push against the edges of an optical disc upon which the protector is mounted.
In embodiments of the invention, the lip does not contain a clasp for grabbing against the side of the optical disc opposite from the side against which the disc-facing side of the main surface is designed to lie. In some embodiments, the optically clear material of which the main surface is made is polycarbonate. In some such embodiments, the polycarbonate is capable of holding an electrostatic charge, and is charged so the main surface is electrostatically attracted to an optical disc on which the disc protector is mounted. In some embodiments, the circular main surface is substantially flat. In others it has a slight dome-like shape to make its peripheral edge resist bending (or lifting) away from the edge of an optical disc upon which the protector has been mounted. This dome-like curvature of the main surface can extend in either of two directions: one which makes its exterior-facing side concave and its disc-facing side convex; or one which makes its disc-facing side concave and its exterior-facing side convex. For purposes of simplification, disc protectors which have this dome-like curvature will often be referred to in this specification and the claims as xe2x80x9cconcavexe2x80x9d, even though they will appear as convex if viewed from the other side.
In some embodiments in which the dome-like curvature makes the disc-facing side convex when the protector is mounted on an optical disc, the flat surface of the disc pushes against the convex curvature of the disc-facing side, tending to deform the disc protector in a way which creates an arch or xe2x80x9cdomexe2x80x9d opposite in shape to the disc protector that is not mounted. This inside-out transformation when mounted on an optical disc utilizes the physical strengths that an arch or a dome provide in resisting the upward lifting of the outer edge, and also pushes the peripheral lip inward so as to increase the tightness with which the peripheral lip grips the edge of the optical disc.
In some embodiments, the thickness of the sheet formed by the circular main surface is between five and seven mils. The optical disc protector can be formed in multiple different ways, including a thermoform process (i.e., vacuum forming) or die 5tamping process. In some embodiments the depth of the peripheral lip, that is the distance by which it extends away from the main surface of the protector, is approximately equal to the thickness of the optical discs which the protector has been designed to cover. In other embodiments, the depth of the peripheral lip is approximately equal to one half the thickness of such optical discs.
According to other aspects of this invention, differing combinations of the above features are provided.